data: Start__Time type sy-uzeit.
data: End__Time type sy-uzeit.

If sy-uzeit < 14400.

*Sets time to zero for four hours
  Start__Time = 0.
*Number of seconds in a day, minus 1
  End__Time = 86399.

Else.
*Sets start to four hours earlier and end to now
  Start__Time = sy-uzeit - 14400.
  End__Time =  sy-uzeit.
Endif.

l_t_range-sign = 'I'.
l_t_range-option = 'BT'.
l_t_range-low = Start__Time.
l_t_range-high = End__Time.